Hanoi plans four-month cleanup operation to revive legendary lake

The state-owned Hanoi Sewerage and Drainage Limited Company is assessing the environmental impacts of a project to clean up Hoan Kiem Lake in the heart of the capital. If approved, the 120-day operation to save the iconic lake would start in late July or early August.

Hoan Kiem Lake, also known as Returned Sword Lake, is severely polluted and has lost its ability to clean itself, said Vo Tien Hung, the company's director.

The quality of the lake's water is declining with a high algae density and a high pH level. The concentration of suspended sediment is above the permitted levels in all five locations where it is monitored, while the concentration of organic pollutants is twice the normal standard. In some places the water has even lost its iconic green color.

Another source of the pollution is the thick layer of mud at the bottom of the lake, according to Hung. In some places, the mud is over 1-meter thick, lowering the water level to only 0.5-0.8 meters. The project would therefore include dredging in addition to water treatment.

“While dredging, we need to preserve the lake's green algae so we have asked scientists to collect the algae so we can put it back later,” said Hung.

Hoan Kiem Lake is one of Vietnam's national heritage sites and a top tourist destination with great historical value, so the cleanup project will need approval from the culture ministry before it can go ahead.

A recent study by the Institute for Environmental Science and Development found that all of Hanoi’s urban lakes and waterways are heavily polluted.

Last October, 200 tons of fish washed up dead due to pollution in West Lake, the city's largest body of water.